The water was murky, the current was swift and the chopper that sputtered and landed upside-down in the East River was sinking like a bag of stones.

It was hard enough trying to rescue the two men who were clinging for dear life to the drowning helicopter's skids.

But there were two women floating unconscious near the wreckage who could do nothing at all to help themselves.

"One woman had a severe head wound, and they were face-down," said police Lt. Larry Serras, 45, one of four members of the NYPD's Emergency Service Unit who dived into the water moments after the sightseeing helicopter plunged into the river.

"I was trying to concentrate on the women. We were all clumped together, never separated. We bundled the flotation devices into one spot. It was not easy to tread water. We had three flotation devices.

"The detectives held the women face-up out of the water. It was tricky. It was not an accurate process. It was tough. We were losing control."

They quickly got help from rescue workers about 50 yards away, on a pier.

They threw their colleagues a rope and pulled on it, hand over hand, to help everyone get to shore.

Meanwhile, the chopper was still sinking, and there was a woman inside.

"When I looked at the helicopter, all I saw was the pilot," Serras said, hours after the rescue.

"He was yelling to us that there was an additional person trapped in the helicopter. By the time we arrived, the helicopter was under. I stood on it for a brief second before it slipped away from me on my feet."

They couldn't get her out.

When divers finally caught up with the chopper at the bottom of the river, they found the body of 40-year-old Sonia Marra Nicholson still inside.

"She was unbuckled," said NYPD diver Jason Gregory.

She had been trying desperately to get out.

Serras and his crew had been on the West Side, engaging in some counterterrorism tactical training, when the call about the helicopter came crackling through on their radios.

Serras didn't mind saying that they drove nearly 80 mph to get to the scene, where they had to dump their bulletproof vests, Kevlar helmets and gun belts before they dived into the water in full uniform.

"The water wasn't cold but the current was strong," Serras said. "The pilot did indicate that someone was inside, but at that point, the helicopter had submerged and there was no way we could get to it."

"We did what we could," said James Coll, an ESU detective who helped guide the unconscious women and the two men to safety.

As traffic hummed above on the FDR Drive and rescue boats circled the chaotic crash scene, emergency workers frantically performed CPR on victims at a makeshift command center on a landing pad.

ESU Detective Keith Connelly said they had started chest compressions on the women even before they were out of the water.